Organic-inorganic hybrid perovskite materials possess advantages over other candidate classes for chemo-sensory materials because of their structural tunability and stability. In this work, we prepared highly qualitied MAPbBr 3 perovskite crystals to provide a high carrier mobility to enhance the sensing on gas, where the response time of sensing below 0.1 s is obtained. Because the perovskite field effect transistor provides a large surface to adsorb gas, the sensitivity of detection can reach 0.2 ppm. Furthermore, combining with theoretical simulation, we analyzed the binding energy, electronic structure, and charge transfer density between perovskite surface (including PbBr 2 -terminated surface and CH 3 NH 3 Br-terminated surface) and gas molecules to study the mechanism behind the phenomena. It is obtained that enhancing the interfacial charge transfer density and then suppressing the recombination of transferred charges will effectively increase the sensitivity of the sensor. • Self-powered MAPbBr3 sensor presents a fast response on sensing, below 0.1 s. • The sensitivity of detection can reach as high as 0.2 ppm. • Perovskite sensor presents different response when the gas is changed.